Weil-McLain -230 - Manual (Page 10)

Part number 550-100-029/0404
GAS
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FIRED WATER BOILER SERIES
2 — Control Supplement
10
Operating information
(continued)
• For ODT above 32°F:
• Set Parameter 4 to the desired system temperature when
outdoor temperature is 32°F.
Reset curve
Figure 5 shows how the Ultra control module calculates
target temperature.
• For outdoor temperature at or below 32°F, the target
temperature equals Parameter 4 and never higher.
• For outdoor temperature above 32°F, the target
temperature is reduced on a curve that would result
in 70°F supply temperature at 70°F outdoor
temperature.
Summer/winter switch option
Install a summer/winter switch, if desired, to disable the
boiler (space heating) circulator during non-heating
months. Connect switch across the outdoor sensor
terminals. When switch closes, the boiler circulator is
disabled and the boiler operates only on call for DHW
heating.
Supply temperature boost
In outdoor reset operation (outdoor sensor connected),
the Ultra control module automatically increases the
target outlet water temperature if a call for heat exceeds
10 minutes. At each 10 minutes of a continuous call for
heat, the control module increases the target temperature
by 18°F. The module will continue increasing target
temperature until it reaches the value set in parameter 4.
When the call for heat ends while target temperature is
“boosted,” the target temperature drops about 2°F for
each minute the thermostat is open.
Purpose of boost — If the target temperature happens to
be too low, the control “boosts” the target temperature
until the supply water meets the system’s needs.
Figure 5 Outdoor reset target temperature
DHW operation, if used
The PhD Control Module allows connection of a
DHW aquastat to low voltage terminal strip terminals 3
and 4. When the DHW aquastat calls for heat, the module
shuts down the boiler circulator, activates the DHW
circulator and immediately sets target outlet water
temperature to 190°F. This provides automatic priority
heat allocation to the indirect water heater for maximum
response and recovery. The DHW circulator continues
for 30 seconds after the heating cycle to deliver the most
possible heat.
Boiler circulator
Each Ultra boiler is shipped with a circulator. The
circulator has sufficient head to handle boiler pressure
drop plus reasonable pressure drop in the connecting
piping. See Ultra Boiler Manual for piping and flow rate
information. The control module internal relay contact
is suitable for handling only the boiler circulator provided.
Do not wire additional pumps in parallel with the boiler
circulator. To operate a system circulator when the boiler
circulator operates, see pages 4 and 5 for wiring required.
Freeze protection
DO NOT install the boiler in a room likely to freeze.
The following integral feature of the Ultra control module
provides some protection for the boiler only — not for
the system.
• The Ultra control module provides freeze-up
protection as follows when the boiler water
temperature drops below 45 °F:
• Below 45 °F, the boiler circulator operates constantly.
• Below 37 °F, the boiler turns on at low fire.
• Boiler and circulator turn off if boiler water temperature
rises above 50 °F.
This feature of the Ultra control module
does not eliminate the possibility of freezing.
The installation must still use recognized
design, installation and maintenance
practice to prevent freeze potential for the
boiler and system.
External controls (interlocks)
(if used)
External limit controls wired between low voltage
terminal strip terminals 6 and 7 will cause the boiler to
shut down in soft lockout when they open. Remove the
factory jumper between these terminals when using.
External limit control wired between low voltage terminal
strip terminals 6 and 8 will cause the boiler to hard lockout
(requiring manual reset of the electronic display RESET
button). Remove the factory jumper between these
terminals when using.
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